Various nutrient elements are necessary for growth of plants. It is known that a lack of some of the elements causes hindrance in the growth of plants. For example, the big three fertilizer components function as follows. Nitrogen is a component element of proteins, and phosphorus is a formation element of nucleic acid or phospholipid and further plays an important part in energy metabolism and synthetic or decomposing reaction of a substance. Potassium has a physiological action of substance metabolism or substance migration. If these main components are lacking, the growth of plants generally becomes poor. Calcium is an important component constituting plants and cells, and further plays an important part in maintenance of the balance of the metabolic system. The lacking state of calcium causes physiological troubles. Besides, various nutrients as follows are necessary for plants: magnesium, iron, sulfur, boron, manganese, copper, zinc, molybdenum, chlorine, silicon, sodium and the like.
Nutritious components such as nitrogen, phosphorus and potassium are applied as basal fertilizer or additional fertilizer. Alternatively, they are applied by diluting liquid fertilizer and irrigating the diluted fertilizer into soil or by spraying the diluted fertilizer onto phylloplanes. These fertilizers are necessary and/or essential for the growth of plants. However, even if they are applied at larger concentrations than some values, the growth of plants and the yield of the plants cannot be further improved.
However, it is an important theme in agricultural production to promote the growth of agricultural plants and increase the yield per unit area to strive for an increase in income. Various plant growth regulators have been developed and used to help meet this need. The plant growth regulators, the typical examples of which include gibberellin and auxin, are used to regulate growth reactions or form-producing reactions such as germination, rooting, expansion, flowering and bearing. When these regulators are used, a period or a concentration thereof for applying these regulators and a method of treating these regulators are complicated. Thus, the uses thereof are restrictive.
In order to solve such problems, JP-A 55-100304 discloses that a plant growth regulator characterized by comprising an organic acid as an effective component is useful for graminoids, leaf vegetables and root vegetables. JP-A 62-242604 also discloses that a composition for regulating plant growth, which comprises lactic acid, is useful for promoting growth and/or production of fruits and suppressing growth of undesired plants.
Furthermore, U.S. Pat. No. 5,482,529 discloses a preparation for fertilizer comprising a plant nutrient, water, a lipophilic organic material and a fatty acid having 1 to 10 carbon atoms in order to improve absorbing phosphoric acid. JP-A 4-31382 also discloses that propionic acid or a polyhydric carboxylic acid makes a phosphoric acid-absorbing effect high.
JP-A 9-512274 discloses a method for regulating plant growth which comprises suppressing a height of the plant by applying a growth-suppressing composition comprising a polyol in an effective amount for growth-suppression to a root sphere of the plant and then increasing the diameter of its stem.
In the present situation, however, none of the above-mentioned techniques can be said to be sufficient in their effects for practical use.